Scientists working on an international assessment of the latest scientific research about climate change said Monday that there is mounting evidence that human activity is contributing to global warming, despite some gaps in knowledge.

Here are some key questions and answers about the panel and its assessment.

What is the IPCC?

The United Nations Environment Programme and the World Meteorological Organization created the Intergovernmental Panel on Climate Change in 1988 to produce assessments for governments on the latest scientific evidence about global warming. Scientists volunteer their time to write and review chapters in the reports that provide summaries of climate change impacts, future risks, options for adaptation and mitigation. Since its creation, IPCC authors have come under attack by some who have accused them of exaggerating evidence or even making it up. But every line in the assessments is subject to a review by governments that verify whether it is based on scientific literature. The review process also allows for comments and a discussion to determine the degree of confidence in each statement.

The first part of the panel’s fifth assessment report is scheduled for release on Friday, following a final review of evidence of climate change and its causes.

What will this week’s report say?

Qin Dahe, a glaciologist from China who co-chairs a working group that is producing the report, opened the final review process Monday by saying that the scientific evidence about the human influence on global warming has “strengthened year by year, leaving fewer uncertainties about the serious consequences of inaction, despite the fact that there remain knowledge gaps and uncertainties in some areas of climate science.”

The other co-chair, Thomas Stocker, a professor of climate and environmental physics from Switzerland, said the assessment is based on millions of measurements “which permit an unprecedented and unbiased view of the state of the Earth System” compiled in a document “with no compromises to scientific accuracy.”

Draft versions of the assessment, according to media reports, say scientists now conclude it’s “extremely likely” — that is, a 95 per cent probability — that humans are the main cause of climate change observed since the 1950s, primarily through their burning of fossil fuels such as oil and coal. The draft said there was “high confidence” that the changes were responsible for warming the ocean, melting snow and ice, raising sea levels and changing some climate extremes, Reuters reported on Monday.

The draft represents the strongest warning from the IPCC that human activity is linked to global warming since the panel was first created.

I read on the Internet that scientists admitted they had overestimated global warming, so how can we know these guys aren’t exaggerating in the new report?

The 2007 report estimated that temperatures had warmed at a rate of about 0.13 C per decade from 1951 to 2005, and at a rate of about 0.2 C per decade since 1990.

Draft versions of the 2013 assessment reportedly say that the warming per decade since 1951 is now 0.12 C, a difference of about 0.01 C, and that warming over the past 15 years has been at a rate of about 0.05 C per decade. This last estimate appears to be one-quarter of of the previous short-term warming trend estimated in the 2007 report. But three different climate scientists contacted by Postmedia News say it is misleading to compare those numbers, saying it is normal to see fluctuations in trends over shorter periods of time, such as within a single decade.

Reuters said Monday that the draft version of the assessment says, with deep cuts to greenhouse gas emissions, warming could be held to an increase this century ranging from 0.3 C to a maximum of 4.8 C, with sea level rises of between 26 to 81 centimetres, before the year 2100. A range of temperature increases of 1.1 to 6.4 C, projected in the 2007 report, was based on older computer models, the news agency reported.

Gavin Schmidt, a climate scientist from NASA’s Goddard Institute for Space Studies, described other recent media reports suggesting that forecast warming trends were being downgraded by scientists as “nonsense.”

“It’s just people randomly picking out numbers… without any kind of understanding of whether they were comparing apples to oranges.”

Andrew Weaver, a climate scientist who was elected this year as a Green Party member of the British Columbia legislature, contributed to one of the chapters of the assessment and said that some warming trends may not be as strong as expected in recent years because of heat being absorbed in oceans. But he said that some “vested interests” are trying to make it seem as though scientists are toning down their earlier forecasts to create a “distraction” from the evidence.

What do Canadian government scientists say about all this?

Environment Canada said in an internal 2012 presentation that climate models “clearly” show that all emissions scenarios will lead to global warming of about two degrees Celsius above pre-industrial levels by 2050. Prime Minister Stephen Harper and other world leaders have signed an international agreement that requires countries to avoid passing this threshold based on evidence that it would cause widespread disruptions to life on Earth with significant repercussions for the global economy.

The department declined interview requests with its climate scientists Monday, explaining that it wouldn’t consider any media requests prior to the IPCC report’s release on Friday.

I also heard that global cooling is about to happen. Isn’t the ice recovering in the Arctic?

Some media outlets have recently reported a change in ice cover over the past year, without providing the context of longer-term trends.

Arctic sea ice for the summer reached a record low in 2012, according to the Colorado-based National Snow and Ice Data Center. Sea ice levels were higher over the summer of 2013, but the total was more than one-million square- kilometres below the average level observed between 1981 and 2010, according to the centre, based at the University of Colorado Boulder.

Weren’t there mistakes in the last IPCC report?

A section of the 2007 IPCC report incorrectly said that scientific evidence had concluded Himalayan glaciers could melt away by 2035. The IPCC faced a public relations nightmare following revelations of the mistake, attributed to quoting sources from a media report instead of a scientific journal. At the time, the IPCC said it regretted the poor application of its well-established review procedures in the drafting of the assessments. But at the time, senior IPCC officials downplayed the mistake, saying it didn’t damage the overall credibility of the 3,000-page report, while noting that the melting of glaciers is accelerating and will affect the supply of water in major mountain ranges where more than one-sixth of the global population lives.

But anticipating more scrutiny, most climate scientists have suggested that the final report in 2013 will use more conservative language throughout all of its chapters, to avoid repeating the same mistake.

As the sea levels around the globe rise, researchers affiliated with the National Science Foundation and other organizations are studying the phenomena of the melting glaciers and its long-term ramifications.